Why did LB Cam Johnson slide to the seventh round?

As the Dolphins outside linebackers coach from 2008-09, Reid worked with Jason Taylor and Joey Porter, a duo with 10 combined Pro Bowl appearances. Johnson has the talent to mirror their careers, Reid said.

“I’m just going to tell you right now, this young man, Cam Johnson, has as much ability as anyone I’ve coached in the NFL,” Reid said. “In my two years there, I was so impressed with the people there in Miami and it’s the same with Cam Johnson.”

The rantings of a fiercely loyal college coach? It’s possible. But Reid wasn’t the only who pegged the 49ers’ seventh-round pick as a much higher selection.

So what caused Johnson to nearly tumble out of the draft — he was a selected 16 spots before Mr. Irrelevant?

For starters, Johnson did not have eye-popping production in college. A starter in 34 games, he had 12.5 sacks, averaged 41 tackles in his final three seasons and never was recognized by the conference for all-ACC honors.

In addition, Rang said Johnson may not have a natural position in the NFL. Due to a coaching change after his sophomore year, Johnson moved from a 3-4 outside linebacker to a 4-3 defensive end his final two years. He’s versatile, but he may not be ideally suited for either spot in the pros.

“My concern with Cam Johnson is I think he’s a little bit of a tweener,” Rang said. “By that I mean he’s a little too big and he’s not quite as fluid as I would generally like a 3-4 outside linebacker to be. But he’s not quite stout enough at the point of attack as a run defender to be a traditional 4-3 defensive end. That’s my biggest concern about him.”

Still, as Rang noted, Johnson would seem to have too much natural talent to slide so far. With his blend of size and speed (4.78 40-yard dash), the former high school wide receiver and safety has a much-coveted skill: Natural pass-rush ability, which Porter and Taylor, both third-round picks, also possessed out of college.

“Joey Porter and Jason Taylor weren’t highly drafted guys,” Rang said. “So I think that’s one of the things that make that comparison interesting.”

Another reason Johnson could have dropped is his medical file. At Virginia, he was diagnosed with sickle-cell trait, a genetic disorder that can affect blood hemoglobin and cause anemia during extreme physical exertion.

In a phone interview this week, London struck a different note. He said he didn’t think Johnson’s sickle-cell trait was a major issue during his career. He also praised his desire, noting he played the entire season — and never begged out of practice — with a deep bruise of his left kneecap that he suffered in summer workouts. When the injury forced him to miss a game against Idaho, Reid said Johnson, unable to push off his leg, cried during pre-game warmups.

Johnson did play 566 snaps as a senior after averaging 803.5 snaps his previous two years. Both London and Reid said they used a three-man rotation at defensive end last year because they had three capable players, not due to Johnson’s sickle-cell trait.

Johnson declined to discuss his sickle-cell trait during college, but he did talk about his condition in a phone interview Tuesday. A basketball and football star in high school, Johnson said it has never caused him to leave a game, at any level.

“For me, fatigue sets in as much as it does for any other player,” he said.

After the draft, 49ers general manager Trent Baalke said Johnson’s sickle-cell trait could have caused him to drop, but he didn’t think it would be an issue during his NFL career.

Reid, of course, agrees. And he believes Baalke — and his staff — made the ultimate draft heist when they plucked Johnson in the final round.

“They ought to put (49ers director of college scouting) Joel Patten in jail for stealing a player,” Reid said.